I have been in the building trade and always believed you numbered from ground floor road entrance side.Otherwise if there were 3 floors below ground level at the back you would have to ask to be on level 4 to have a first floor flat on the front.
I firmly believe this shoud have been pointed out when buying.I think most people who asked to be on the second floor back or front needed telling how they where being marked out.
It seems if the garage is above ground .this then qualifies for ground floor.In this case you could be on level two at the front and still end up with an apartment on the ground floor.
In my opionion if you ask for a second floor apartment golf side you should be two foors above the ground.Like wise if you ask for a second floor flat on the front you should be two floors above ground level.